In a filter assembly machine, the advantages of feeding a succession of pairs of side by side double cigarette portions to a rolling drum of the filter assembly machine are known, for example, from EP-B-110836.
As described in the above patent, the succession of pairs of side by side double cigarette portions is formed by feeding the double cigarette portions along a transfer unit located at the input of the filter assembly machine and comprising two feed lines, each of which feeds a respective single succession of double cigarette portions to specific points on an output drum located upstream from a rolling drum of the filter assembly machine.